Grinding machine

ABSTRACT

A grinding machine for grinding workpieces by abrasive particles with at least one grinding unit having two parts rotatable relative to one another, is characterized in that in a container for receiving articles to be ground is located in rotary manner a disk, that on the container below the disk is provided a rotary drive for the latter and that the axes of the disk and rotary drive are aligned.

[0001] The invention relates to a grinding machine for grinding workpieces by means of abrasive particles with at least one grinding unit having two parts rotatable relative to one another.

[0002] For example centrifugal force sliding grinding machines are known comprising a two-part container with a tray-like, rotary, base-forming container bottom and a stationary, cylindrical container top.

[0003] Such grinding machines are used for the surface working of articles to be ground or workpieces, e.g. smaller parts, which are moved together with the abrasive particles and optionally a liquid process medium in the container. If the bottom is rotated, the workpieces to be treated are moved outwards on the disk until they strike the inner wall of the container against which they are decelerated. As a result of the afterflowing workpieces a revolving workpiece movement arises bringing about an intense grinding or polishing action.

[0004] Such grinding machines have hitherto been used professionally in production workshops for the article to be ground, such as jewellery and other parts to be polished. They consequently have a complicated design and construction and are correspondingly expensive. The problem of the invention is to provide a grinding machine of the aforementioned type, which is inexpensive and which can consequently be used in further sectors, particularly in sales outlets for the article to be ground or can be employed by private individuals for polishing jewellery.

[0005] According to the invention, in the case of a grinding machine of the aforementioned type, the problem is solved in that in a container for receiving the article to be ground a disk is arranged in rotary manner, on the container and below the disk a rotary drive is provided for the latter and the axes of the disk and the rotary drive are aligned.

[0006] As a result of this preferred solution it is possible to make a grinding machine easy and inexpensive to produce. This is helped by the fact that the disk is connected in non-rotary, bearing-free manner to the driven shaft of the rotary drive. As a result of this preferred solution there is no need to provide an additional mounting support for the driving shaft of the rotary disk, in addition to the mounting support for the driven shaft of the rotary drive, no matter whether the latter is a driving motor or a geared motor with an integrated motor and integrated gear. Preferably the disk is connected by a coupling piece to the driven shaft of the rotary drive and in particular the coupling piece has aligned bores, through which project the driven shaft of the rotary drive and a centring pin of the disk. According to a further development the coupling piece and driven shafts are interconnected in non-rotary manner by a radial locking screw and the rotary disk and the coupling piece are interconnected in non-rotary manner by screws. A further development is characterized by a dust-tight and/or liquid-tight passage of the disk drive through the container base and the coupling piece is more particularly held in axially secure manner in containers by shaft-sealing rings, so that an optimum sealing action is obtained.

[0007] According to further developments of the invention, the rotary drive is held in a foot part and is firmly connected to the latter by screws and the fastening screws for the rotary drive are oriented parallel to the axis.

[0008] The disk is not completely planar and instead optionally has an edge raised above its base. Thus, as a function of its material and that of the container wall the disk can be spaced from the latter or can be pressed against the edge under centrifugal force. On the underside the disk has a finite spacing relative to the container base. The size of the lateral, radial gap, if one is provided, is smaller than the axial spacing of the disk from the container base. This ensures that it is only possible for particles to pass beneath the disk which are much smaller than the spacing of the disk from the base.

[0009] Particularly when the grinding machine according to the invention is constructed as a liquid grinding machine with a liquid process medium in the container, according to a preferred development the entire disk is rigid. According to a further development in this case, the width or thickness of the gap is at least {fraction (1/10)} mm and generally should not exceed 2 mm. It has surprisingly been found that in the case of a centrifugal sliding grinding machine according to the invention with liquid located in the container said liquid is expelled from the gap between the rotary disk and the stationary container base and no liquid is located there. This ensures that no article to be ground passes into this area and this includes broken off fragments of larger grinding bodies and which would lead to a deterioration of the mounting of the disk or the disk drive shaft passed outwards through the base.

[0010] The same effect, namely the prevention of the penetration of grinding bodies or fragments thereof or the expulsion of the same from the gap between the rotary disk and the stationary base can be achieved in a dry-working centrifugal grinding machine, i.e. a dry grinding machine, in that the disk has resilient material, at least on its underside.

[0011] As a result of the inventive design of the disk, it is also ensured that when a grinding body or grinding article particle penetrates into the gap it is merely conveyed outwards again through the relative rotary movement between disk and container base and as a result of the resilience of the disk or its underside no wear arises and it is in particular ensured that the mounting support of the disk is not impaired.

[0012] The invention makes it possible to design and construct very inexpensive and operationally reliable centrifugal force sliding grinding machines, which permit the use of very fine grinding and/or polishing materials.

[0013] According to another preferred development a drive shaft of the grinding disk is passed in liquid-tight manner through the container base.

[0014] The disk or the layer on its underside can e.g. be of an elastomeric plastic and in particular rubber, but it is also possible to use felt, cotton fabric or a standard resilient base covering, such as a PVC floor covering or carpeting of any type.

[0015] According to a preferred development the disk has an upwardly raised circumferential edge. Over most of its surface the disk has a planar base and only the edge is raised somewhat, so that a circumferential edge projecting over the container base is provided thereon.

[0016] If in the case of smaller disks, e.g. up to approximately 250 mm diameter, it is possible to provide an abrading seal between the disk edge and the surrounding cup part, as a result of the limited wear susceptibility of the inventive centrifugal force sliding grinding machine associated with the flexible disk, the gap can be larger than the minimum dimensions of the grinding or polishing material particles. However, it remains of the same order of magnitude and should in particular be no more than two or three times larger, so that during the operation of the grinding machine they can pass under the disk and as a result of the relative movement of the flexible, rotating disk with respect to the container base can be released again and transported radially outwards towards the container wall.

[0017] With very fine polishing material, such as walnut granules, the gap should also be very small. With coarser granules, the gap width b is preferably at least 2 mm and at a maximum preferably roughly between 3 and 4 mm. The gap width can in particular be variable so that it can be adapted to the granules used. The gap adjustability can be brought about by random known means, e.g. by washers or the like located between the container base and the disk. The gap can also be adjusted e.g. via setscrews, by means of which a shaft traversing the container base for the mounting support of the flexible disk can be vertically adjustable and fixed in a desired height.

[0018] Another preferred development is characterized in that a closable outlet is provided below the disk in the container base.

[0019] According to another preferred development, the casing is in one piece and in particular the casing and/or container is made from plastic. Thus, the grinding machine according to the invention can be manufactured economically and therefore inexpensively. This is helped by the fact that the rotary drive is placed below the disk.

[0020] As a result of the grinding unit design according to the invention it is possible to have in a machine several grinding units at limited design and constructional cost, so as to e.g. permit the rational working of heavier and/or impact-sensitive workpieces, which do not allow a joint working of several workpieces in a single container. A grinding machine according to the invention can in particular be used for the dry polishing of jewellery, dental parts, etc.

[0021] Further advantages and features of the invention can be gathered from the claims and the following description of an embodiment with reference to the single attached drawing showing a preferred development of the grinding machine according to the invention in longitudinal section.

[0022] The grinding machine 1 has a one or two piece casing 2′ with a container 2 and a foot 2″ and where optionally the container 2 and foot 2″ in each case form part of the two-piece casing 2′. The casing is preferably made from plastic and this more particularly applies to the container 2. The container 2 contains a disk 3. In the embodiment shown the disk 3 has an upwardly sloping, raised circumferential edge 3 a, whose outer wall follows the contour of the container 2 in this area. Thus, between the disk 3 and the container base 2 a is formed a finite spacing 5 of size b, which has essentially the same dimension over the entire disk surface. As a result of the upwardly drawn disk edge 3 a a dish-shaped receptacle for the article to be ground is created. A gap 5 a, smaller than the spacing 5, is formed between the disk edge 3 a and the container wall 2 b.

[0023] Below the disk 3 a rotary drive 11 for the latter is provided in the foot 2″. The rotary drive can be a motor directly driving the disk 3 or also a geared motor with integrated gear. The rotary drive 3 has a vertically upwardly directed-driven shaft 12. The rotary drive 11 is fixed to the casing 2′ by screw connections 13 a directed parallel to the shaft 12 and via a mounting plate 14. In a bore of the casing 2′ between foot 2″ and container 2 is provided a coupling piece 15 by means of which the disk 3 is connected in non-rotary manner to the driven shaft 12 of the drive 11. For this purpose the coupling piece 15 has bores 15 a, 15 b. The driven shaft 12 of drive 11 projects into bore 15 a. A radial locking screw 16 is provided for the non-rotary connection. Into bore 15 b projects a centring pin 17 firmly connected to the disk 3. A non-rotary connection between the disk 3 is brought about by screws 18 engaging in the coupling piece 15 parallel to the centring pin 17.

[0024] Alignment takes place between axis A of disk 3 and rotary drive 11. The bores 15 a, 15 b can also be a through bore. Below the coupling piece 15 the driven shaft 16 of the rotary drive 11 is surrounded by a centring ring 19. A hardened ring 21 is firmly connected to the coupling piece in the upper area thereof. The coupling piece 15 is axially secured in the casing 2′ by shaft-sealing rings.

[0025] The disk can have a rigid construction if working takes place with liquid in the container. However, for wet and dry working, the disk is made from a flexible material, such as rubber or plastic. The disk is spaced from the container base 2 a, accompanied by the formation of a gap 5, the gap width b being e.g. approximately 3 mm for dry working. For example, accompanied by a variation in the gap width, the disk 3 and/or container 2 can be positioned in vertically adjustable manner. During the operation of the grinding machine the comparatively wide gap small particles of the article being ground or in particular the grinding material can pass between the disk and the container base and as a result of the rotary, flexible disk are again conveyed in the direction of the container wall 2 b, without there being any significant wear to the container base 2 a or disk 3. As a result of the flexible disk 3 the amount of frictional heat produced is significantly reduced, because any abrasive particles which have passed below the disk 3 are conveyed radially outwards instead of being crushed. Additionally, laterally in the base 2 a of the container 2 can be provided a closable outlet 23 for draining off liquid and expelling any material present there prior to the end of the operation. As a result of the inventive design with aligned axes A of rotary drive 11 and disk 3, a constructionally simple grinding machine 1 is created, which can be manufactured at low cost and can be sold at a low price, so that it can also be used in the private sector for polishing jewellery. LIST OF REFERENCE NUMERALS  1 Grinding machine  2 Container  2′ Casing  2″ Foot  2a Base (of 2)  2b Container wall  3 Disk  3a Disk edge  5 Spacing  5a Gap 11 Rotary drive 12 Driven shaft 13 Screw connection 14 Mounting plate 15 Coupling piece 15a, 15b Bores 16 Locking screw 17 Centring pin 18 Screws 19 Centring ring 21 Hardened ring 22 Shaft-sealing rings 23 Outlet A Axis B width 

1. Grinding machine for grinding workpieces by means of abrasive particles with at least one grinding unit having two parts rotatable relative to one another, characterized in that in a container (2) for receiving the article to be ground is placed in rotary manner a disk (3), that on the container (2) below the disk (3) is provided a rotary drive (11) for the latter and that the axes (A) of disk (3) and rotary drive (11) are aligned.
 2. Grinding machine according to claim 1, characterized in that the disk (3) is connected in bearing-free, non-rotary manner to the driven shaft (12) of the rotary drive (11).
 3. Grinding machine according to claim 1 or 2, characterized in that the disk (3) is connected by means of a coupling piece (15) to the driven shaft (12) of the rotary drive (11).
 4. Grinding machine according to claim 3, characterized in that the coupling piece has aligned bores (12 a, 12 b) into which project the driven shaft (12) of the rotary drive (11) and a centring pin (17) of the disk (3).
 5. Grinding machine according to claim 3 or 4, characterized in that the coupling piece (15) and driven shaft (12) are interconnected in non-rotary manner by a radial locking screw (16).
 6. Grinding machine according to one of the claims 3 to 5, characterized in that the rotary disk (3) and coupling piece (15) are interconnected in non-rotary manner by screws (18).
 7. Grinding machine according to claim 6, characterized in that the coupling piece (15) is held in axially firm manner in the container (2) by shaft-sealing rings (22).
 8. Grinding machine according to one of the preceding claims, characterized in that the rotary drive (11) is held in a foot part (2″) and is firmly connected thereto by screws (13).
 9. Grinding machine according to claim 8, characterized in that the fastening screws (13) for the rotary drive (11) are oriented parallel to the axis (A).
 10. Grinding machine according to one of the claims 1 to 9, characterized by a dust-tight and/or liquid-tight passage of the drive of disk (3) through the base of container (2). 